1. Field of the Invention
The present invention relates in general to an apparatus for converting resolution of an LCD (Liquid Crystal Display) monitor, and more particularly to an apparatus for converting resolution of an LCD such that when a resolution of an image provided from an LCD monitor is low, it is converted according to a resolution of the LCD monitor by using a DCT (Discrete Cosine Transform) and an IDCT (Inverse Discrete Cosine Transform).
2. Description of the Prior Art
Generally, a LCD monitor has advantages in that it is light and can be made thin and an image is displayed usually clearly without distortion, so that its application is being extended for coverage including lap-top computers. Accordingly, it is necessary to convert the resolution of an image output from a computer the a resolution of the LCD monitor. When converting the resolution to that of the LCD monitor, a level of a color signal of predetermined R, G and B image signals provided from the computer to be displayed on a screen of the LCD monitor are amplified, brightness adjusted and converted to a digital signal. Then a microcomputer in the LCD monitor detects the operating mode of the computer by detecting the frequency of a horizontal synchronous signal and a vertical synchronous signal in order to recognize the image resolution. The resolution is recognizable because the frequencies between the horizontal synchronous signal and the vertical synchronous signal provided from various computers are different from each other according to the display graphics mode of the computer.
The computer may output the horizontal synchronous signal and the vertical synchronous signal in several ways that include separating to output the horizontal synchronous signal and the vertical synchronous signal; outputting a composite synchronous signals by mixing the horizontal synchronous signal and the vertical synchronous signal; or mixing and outputting the horizontal synchronous signal, vertical synchronous signal and R, G or B color signals.
The display graphics modes include: CGA (Color Graphics Adapter) mode; VGA (Video Graphics OuTay) mode; and SVGA (Super Video Graphics Array) mode. The frequency and resolution of the horizontal synchronous signal and the vertical synchronous signal are different for each of these modes. For example, in the CGA mode, a frequency of the horizontal synchronous signal is 15.75 KHz while that of vertical synchronous signal is 60 Hz and a resolution is 640.times.350. In the VGA mode, a frequency of the horizontal synchronous signal is 31.5 KHz while that of the vertical synchronous signal is 60 Hz or 70 Hz, and its resolution is 720.times.350 or 640.times.480. In the SVGA mode, a frequency of the horizontal synchronous signal is 35-37 KHz while that of the vertical synchronous signal V is interlaced, and its resolution is 800.times.600.
As described above, when the microcomputer recognizes the resolution according to the display graphics mode, the separated horizontal synchronous signal and the vertical synchronous signal are output to a graphic controller in the monitor. The graphic controller varies divided values of a PLL (Phase Locked Loop) circuit according to the resolution recognized by the microcomputer, and adjusts a frequency of a pulse signal applied to an LCD panel so as to control the display. The LCD panel may provide a resolution of 1024.times.768. Thus, when an image with a resolution of 640.times.480 or 800.times.600 is applied, the graphic controller applies an artificial signal satisfying the resolution of 1024.times.768 to convert the image signal resolution to the resolution of 1024.times.768 and then outputs it to the LCD panel to be displayed. Namely, when an image with resolution of 640.times.480 is applied to an LCD panel with resolution of 1024.times.768, an actual picture through the LCD panel is converted to the resolution of 1024.times.768 through a resolution adjusting unit. In order to display the input image, additional pixels are inserted by the resolution adjusting unit, which has bad influence on the picture quality to be actually displayed. Therefore, in the conventional apparatus for converting resolution in a LCD monitor, when an image with a resolution of 640.times.480 or 800.times.600 is applied, this applied signal is converted to resolution of 1024.times.768 by simply fitting the size of the image to the LCD panel, thus the picture to be displayed is not clear.